There is a need for multiple multi-mode (MMM) low-noise amplifiers (LNAs) for use in radio frequency (RF) wireless communication receiver integrated circuits (ICs), which provide optimal linearity for different operating modes and operating RF bands without impacting IC die area. MMM LNAs may employ multiple transistor gain stages (utilizing RF bipolar or RF field-effect transistors) along with multiple passive components (e.g., inductors) in the input RF matching networks and output RF loads that may occupy a large integrated circuit die area, particularly for lower RF operating bands (450 MHz for example). In addition, each mode of the MMM LNAs may require a separate degenerative inductor between each transistor gain stage and an external ground connection to improve linearity. The value of each degenerative inductor is dependent on the corresponding MMM LNA operating mode gain and linearity required, and may change for different MMM LNA operating modes and MMM LNA radio frequency operating bands.
Wireless communication receiver and LNA operating modes may include different air-interface standards such as GSM, CDMA, and/or WCDMA in the same operating frequency band (US-Cellular receive or US-PCS receive for example, 869-894 MHz or 1930-1990 MHz). Within each air interface standard, the LNA linearity required may change as a function of receive signal strength in the presence of interference (jamming) or whether the transmitter is on or off while attempting to receive weak signals (transmit to receive cross modulation in CDMA mode). In the case of the US-Cellular CDMA air-interface standard, there are three distinct receiver linearity requirements that may require three LNA modes, each with a different gain and linearity requirement. If GSM and WCDMA are also required in the same operating frequency band for the same wireless communication receiver, then a number of degenerative inductors for MMM LNAs will increase proportionally and the overall wireless communication receiver integrated circuit (IC) die area will also increase significantly if the MMM LNAs are integrated.
In the known art, MMM LNA integrated circuit area may be reduced by sharing common load inductors among multiple operating modes and multiple operating frequency bands with corresponding transistors that connect to a common MMM LNA output signal path. However, there may be a corresponding degenerative inductor for each LNA mode to optimize linearity for individual MMM LNA operating modes. In addition, as more operating frequency bands are added to the wireless communication device, the number of multi-mode LNAs and design complexity increases along with the number of degenerative inductors. Furthermore, if each multi-mode LNA is designed as a differential circuit, the number of degenerative inductors doubles. Unfortunately, each additional degenerative inductor impacts overall wireless communication receiver integrated circuit (IC) die area, layout complexity, and RF signal routing.